Sudden cardiac death caused by arrhythmias such as severe bradycardia, asystole, ventricular tachycardia or fibrillation are a major cause of death among the adult population in developed countries. Sudden cardiac death accounts for 1,000 cases per day in the U.S. alone, most of them occurring at home or at the office.
Ventricular tachycardia is characterized by the onset of a very high heart rate. It may be treated by applying a pacing pulse train to the patient's heart with a frequency above the heart rate of the patient and progressively reducing the frequency to a normal frequency corresponding to 60 to 80 beats per minute.
Bradycardia is characterized by the onset of a very slow heart rate. Bradycardia may lead to asystole, commonly known as a flat line, since no cardiac activity is detectable. Bradycardia, or asystole, may be treated by applying a pacing pulse train to the patient's heart with a frequency corresponding to 60 to 80 beats per minute. Bradycardia and asystole are defined as non-shockable rhythms and are not treatable by standard Automatic External Defibrillators (AED).
Ventricular fibrillation can be halted and normal cardiac activity restored by applying electrical defibrillation, or an electrical high energy shock applied to the patient's heart.